Anyone who uses tampons has been taught to fear toxic shock syndrome (TSS). But when it comes to details on the rare, life-threatening infection, most women only really know: 1) it’s bad, and 2) tampons cause it somehow.

We only really hear about TSS when a tragic story makes it into the news. Most recently, four separate cases of TSS were reported in West Michigan within one month, sparking an investigation into the tampon brands used and what could have caused so many cases in one area.

While the condition is extremely rare, it’s true that it can be life-threatening. If you use tampons, there are some things you need definitely should know before your next period.

1. Toxic Shock Syndrome is very rare, but the statistics are spotty.

In the 80s, cases of TSS were the highest, with an incidence of about 10 for every 100,000 menstruating women. After removing a highly absorbent tampon brand from the market, the rates reportedly went down. Current estimates put the rate at one to 17 for every 100,000 menstruating women. According to the Centers for Disease Control and Prevention, only 26 cases were reported in 2015. When you consider that 70 percent of menstruating women use tampons, the incidence rate is really low.

2. TSS starts with the bacteria Staphylococcal aureus.

It's really just a type of staph infection. This bacteria lives on our skin, but it’s when it enters the body through a cut or mucous membrane that it can cause serious infection, explains Mary Rosser, M.D., director for the division of general obstetrics and gynecology at Montefiore Hospital.

3. The staph bacteria produce an endotoxin, called toxin one, which causes TSS.

“One of the effects of this toxin is to cause increased openings in the blood vessels—we call it permeability—that literally causes our blood vessels to leak out fluid into our bodies,” Nichole Tyson, M.D., ob/gyn, and chief of pediatric/adolescent gynecology at Kaiser Permanente, tells SELF. She adds that many women—up to 20 percent—can already have staph aureus in their vaginas. “It is thought that maybe very small tears in the vagina caused by tampons in women who are colonized with Staphylococcal aureus may facilitate this endotoxin into the body’s circulation,” she explains.

The rash is the most telling, as it's a signature symptom and not something that could be mistaken for a stomach virus or flu. It looks like a sunburn, and the skin may continue to peel for a week or two after. “TSS can turn on a dime,” Rosser notes. Within the first few days, it can get bad enough to warrant hospitalization. If it progresses, it leads to multi-organ failure. If you notice these symptoms, call your doctor right away.

5. TSS isn’t just caused by tampons.

Only about half of all TSS cases are menstruation related. Recent surgery, cuts and burns on the skin, recent childbirth, and even some viral infections like the flu or chickenpox can make a person susceptible to TSS. "Other cases have also been associated with diaphragms and contraceptive sponges," says Tyson.

6. The more absorbent your tampon, the higher your risk.

Expert analysis says the more absorbent the tampon, the more bacteria it can hold onto. That, paired with a tiny tear from something like pulling out a dry tampon before it's saturated with blood, can introduce the bacteria into the body. "Use the lowest absorbent type of tampon necessary for your flow," Tyson suggests, to avoid bacteria growth and micro-tears in the vaginal wall. If you need to use super-absorbent tampons because your flow is so heavy, talk to your doctor about ways to get it under control.

It has also been hypothesized that keeping a blood-soaked tampon in for an extended amount of time raises the pH of your vagina—because the vagina is typically acidic, while blood is basic—which makes it easier for the staph bacteria to replicate.

7. The brand of tampon, and whether it's natural or organic, doesn't seem to make a difference when it comes to TSS.

Recently, a few natural tampon brands have hit the market, causing every tampon-user to question if her current arsenal is healthy enough. While there's really no research showing if natural tampons are safer or better for you than traditional ones (tampons are considered medical devices and go through FDA regulations as such, so every one on the market has been FDA approved), neither type will decrease your risk of TSS. Organic or not, wearing a super-absorbent tampon, and wearing it for too long, increases your risk.

8. You should never wear a tampon longer than the box tells you.

OK, real talk. We've all left a tampon in for longer than we should. Sh*t happens, and thanks to tampons' glorious inconspicuousness, it's easy to insert and forget. But the longer it's in there, the more you're putting yourself at risk. "It's very important to talk about it not just as a hygiene issue, but the responsibility of taking care of your cycle," Rosser says. Tampon brands advise 8 hours maximum wear time, but gynecologists will tell you to switch them out sooner than that. If you're using the right absorbency, you should need a fresh tampon every few hours anyway.

9. You can technically sleep with one in, but you do have to be careful.

Again, tampons are technically approved for 8 hours of wear. If there's a chance you may sleep for longer than that, use a pad instead. Rosser suggests wearing a tampon to bed only on the heaviest nights of your cycle, and even then, opting for the lowest absorbency possible and pairing it with a pad for backup. Ultimately, she tells her patients to skip the tampon overnight and sleep with just a pad. "You can sleep with [a tampon], but I think it's better to alternate at least and leave it out when you can," Rosser says. Tyson also tells her patients to wear pads to bed to be safe.

10. If you get TSS, you should stop wearing tampons—period.

Once your vagina has been colonized by the bacteria, your chances of getting TSS again skyrockets. “The recurrence rate can be as high as 30 percent. There is one case report of one woman having five episodes of TSS,” Tyson says. So if the seriousness of TSS isn't motivation enough to practice good tampon hygiene, think about only being able to wear a pad for the rest of your menstruating life.